A conventional example of the diaphragm device has been disclosed in JP-A-2011-27164. Also, a pressure regulating reservoir using a diaphragm device has been disclosed in JP-A-2010-76747.
In the diaphragm device disclosed in JP-A-2011-27164, a protruding portion is provided at a center portion of the lower surface (surface positioned on the lower side during use) of a flexible membrane, and a region where the protruding portion exists becomes a thick portion thicker than the other portion, and a recessed portion is provided at the tip of the thick portion. The recessed portion corresponds to a through-hole formed in a component for supporting the flexible membrane (a through-hole connecting a chamber where one surface of the flexible membrane faces, to the outside), and it is provided for suppressing that the flexible membrane comes into contact with the opening edge of the through-hole and to be damaged.
Also, the pressure regulating reservoir of JP-A-2010-76747 is used for temporarily storing brake fluid discharged from wheel cylinders based on a pressure reduction command from an electronic control device in a brake device for a vehicle capable of performing ABS control (Anti-lock Brake System) or ESC (Electronic Skid Control). If a pump is driven by a motor serving as a driving source, the pressure regulating reservoir becomes a source of brake fluid to the pump.
This pressure regulating reservoir is a variable volume container and includes a piston, which is pressed by the discharged brake fluid such that the volume of a fluid storage chamber increases. Also, in order to continuously supply the brake fluid to the pump even after the fluid storage chamber becomes empty, a diaphragm device is disposed at a portion between the piston and the fluid storage chamber, so that, if the pump operates in a state where the fluid storage chamber is empty, a check valve is opened in the diaphragm device.
The intake of the pump is connected to a main reservoir of the brake device through the check valve. When it is possible to supply the brake fluid from the pressure regulating reservoir, the check valve is closed to disconnect the intake of the pump from the main reservoir, and when the pressure regulating reservoir is empty, the diaphragm device opens the check valve, thereby switching the source of brake fluid to the pump to the main reservoir.
In the diaphragm device provided to the pressure regulating reservoir of JP-A-2010-76747, an abutting member is made of a metal or the like to protect a portion of the flexible rubber membrane facing the opening edge of a through-hole. However, in this structure, the abutting member may collide with a supporting member, thereby generating abnormal noise or damaging the supporting member. Accordingly, the diaphragm device of JP-A-2011-27164 has been proposed.